Collapsible gantry for cranes



Oct. 7, 1969 K- w. RANDALL 3,471,035

COLLAPSIBLE GANTRY FOR CRANES I i r Filed Dec. 4. 1967 a INVENTOR. KENNETH WYQAQDALL United States Patent 3,471,035 COLLAPSIBLE GANTRY FOR CRANES Kenneth W. Randall, Indianapolis, Ind., assignor to Insley Manufacturing Corporation, Indianapolis, Ind., a corporation of Indiana Filed Dec. 4, 1967, Ser. No. 687,663 Int. Cl. B66c 23/06, 23/62 US. Cl. 212-59 1 Claim ABSTRACT OF THE DISCLOSURE Brief description of drawings FIGURE 1 is a side elevation of a gantry crane embodying the invention in a raised position, parts being broken; and

FIGURE 2 is a fragmentary side elevation showing the gantry in lowered or traveling position.

Description of the preferred embodiment There is shown a wheel mounted chassis having a rotating base 11 with a boom 12 pivotally mounted on a bracket carried by the base. A cab 11a is indicated by broken lines. Load lines 12a extend to the boom from hoist drums 12b. On the base 11 are laterally spaced A- frames, each of which comprises an L-shaped lever 13 having an upright leg secured to the base at 15 and a horizontal arm of cantilever 16. At the free end of the cantilever 16 is a pair of laterally spaced rigid plates 16a, which are forwardly and downwardly inclined. Extending downwardly and forwardly between the plates 16a is a leg 17 which has a forked lower end pivoted to a link 18, which in turn is pivoted to the bracket 19 to which the boom 12 is pivoted. Having bearing in the spaced plates 16a of the A-frame respectively is the reduced end portions 20 of a cross shaft 21. Other suitable bracing devices (not shown) are employed to stabilize and strengthen the L-shaped lever 13.

Pivoted at 23 to the apex of each L-shaped lever 13 is an upper arm or rear leg 22, which in raised position of the gantry is vertically disposed. The upperends of arms 22 of the spaced A-frame are connected by a cross shaft 24 on which are mounted the usual cable sheaves 25 and 26, over which cables from hoist drums (not shown) extend to the boom.

Forming part of the gantry are arms 27, which pivotally engage the cross shaft 24 at the upper ends. The lower ends of the arms 27 (for the respective laterally spaced A-frames) have forks 28. The forks 28 fit over the upper ends of the legs 17 to which they are releasably connected by pins 29 suitably retained by cotter pins.

Carried by each cantilever arm 16 of the L-shaped lever 13 is an .air cylinder 30 provided with a bracket 31 suitably pivoted at 32. The piston rod 33 for the 3,471,035 Patented Oct. 7, 1969 ICC cylinder 30 is pivoted to the lower end portion of the adjacent upper leg 22 at 34, provided in a rearward enlargement of the leg 22.

In order to lower the gantry from the raised position shown in FIGURE 1, the pins 29 are first removed thereby to free the respective arm 27, then, by means of the air cylinders 30, the upper rear leg together with the cross shaft 24, sheaves 25, 26 and cables, the gantry is lowered until cradle or recessed portions 35 in the legs 22 rest upon the transverse shaft 21. During this movement the arms 27 follow over laterally projecting guide ledges 36 and 37 on the outer sides of the plates 16a and assume a generally horizontal position, as indicated on FIGURE 2. The air cylinder 30 are two way acting and air under pressure is supplied to opposite ends from any suitable source (not shown). Thus, in the lowered or travel position the gantry is supported by the cantilevers 16.

It will be apparent that raising the gantry is accomplished by the air cylinders 30 which rocks the rear legs 22 to their vertical position at which time the pins 29 and their cotter pins are replaced to connect the arms 27 to the legs 17. Thus by power means the gantry can be conveniently raised or lowered and when lowered the load is sustained by cantilevers.

What I claim is:

1. In a crane, the combination of a base, a boom piv oted to said base, hoist cable system for raising and lowering said boom, an A-frame on said base, said A-frame comprising an L-shaped lever having an upright leg fixed at its lower end and a horizontal arm disposed at right angles to said upright leg and parallel to said base, and constituting a cantilever, -a front leg pivoted at its lower end to said base remote from said upright leg and having its upper end free of but adjacent the terminal end of said horizontal arm, a gantry comprising an upright leg pivoted at its lower end to the apex of said L-shaped lever, an arm pivotally connected at its upper end to the upper end of said upright leg and normally disposed in alignment with said front leg, a detachable connection between the lower end of said pivoted arm and the upper end of said front leg, whereby upon disconnection of said pivoted arm and said front leg the gantry may be lowered and supported by the horizontal arm of said cantilever, fluid pressure means connecting the horizontal arm of said cantilever to said upright leg for raising the gantry and assisting in lowering same, and guide surfaces on the free end of said horizontal arm for guiding the lower end of said pivoted arm in a generally horizontal direction when the gantry is lowered.

References Cited UNITED STATES PATENTS 2,186,372 1/1940 Elgh 212-59 2,774,484 12/1956 White 21259 EVON C. BLUNK, Primary Examiner H. C. HORNSBY, Assistant Examiner US. Cl. X.R. 2l2-144 

